In electrophotographic or electrostatic recording processes, a developer used to form an electrostatic image or an electrostatic latent image can be classified into the following categories: (1) a two-component developer formed of toner and carrier particles; and (2) and a one-component developer formed of toner only. The one-component developer can be further classified into a magnetic one-component developer and a nonmagnetic one-component developer. Fluiding agents such as colloidal silica are often added to the nonmagnetic one-component developer to increase the fluidity of the toner. Typically, coloring particles obtained by dispersing a pigment such as carbon black or other additives in latex are used as the toner.
Methods of preparing toner include pulverization and polymerization. In pulverization, toner is obtained by melting and mixing synthetic resins with pigments and, if required, other additives. This mixture is then pulverized and the particles are sorted until particles of a desired size are obtained. In polymerization, a polymerizable monomer composition is manufactured by uniformly dissolving or dispersing various additives such as a pigment, a polymerization initiator and, if required, a cross-linking agent and an antistatic agent in a polymerizable monomer. Then, the polymerizable monomer composition is dispersed in an aqueous dispersive medium, which includes a dispersion stabilizer. An agitator is used to shape any minute liquid droplet particles. Subsequently, the temperature is increased and suspension polymerization is performed to obtain polymerized toner having colored polymer particles of a desired size.
In an image forming apparatus such as an electrophotographic apparatus or an electrostatic recording apparatus, an image is formed by exposing an image on a uniformly charged photoreceptor to form an electrostatic latent image, attaching toner to the electrostatic latent image to form a toner image, transferring the toner image onto a transfer member such as transfer paper or the like, and then fusing the toner image onto the transfer member using any of a variety of methods, including heating, pressurizing, solvent steaming, and the like. In most fusing processes, the transfer medium with the toner image passes through fusing rollers. By heating and pressing, the toner image is fused to the transfer medium.
Images formed by an image forming apparatus such as an electrophotocopier should satisfy requirements of high precision and accuracy. Conventionally, toner used in an image forming apparatus is obtained by pulverization. In pulverization, color particles having a large range of sizes may be formed. To obtain satisfactory developing properties, the color particles must be sorted according to size to reduce the particle size distribution. However, it is difficult to precisely control the particle size and the particle size distribution using a conventional mixing/pulverizing process in the manufacture of toner suitable for an electrophotographic process or an electrostatic recording process. Also, when preparing a fine-particle toner, the toner preparation yield is adversely affected by the sorting process. In addition, there are limits to changes or adjustments that can be made to the toner design while still obtaining desirable charging and fusing properties.
Using polymerization, the size of particles is easier to control. In addition, these particles do not need to undergo a complex manufacturing process such as sorting. Polymerized toner having a desired particle size and particle size distribution can be obtained without pulverizing or sorting. However, the particle size and shape are not always satisfactorily controlled. In addition, it is not always easy to agglomerate latex and colorant. Further, an aluminum-based material may be used as an agglomerating agent, which is hazardous to human health and the environment. Also, since the toner has a narrower fusing range as the printing speed increases, toner having different fusing properties according to the printing speed, may be needed.
Therefore, there is a need for toner that is efficiently agglomerated, presents little or no risk to humans or the environment, forms images having high glossiness, has a wide fusing range during a high-speed printing operation, has a fine particle size and reduced particle size distribution and has excellent heat preserving and anti-offset properties.